PROJECT SUMMARY/ ABSTRACT Psychiatric disorders are the leading cause of mortality and disability among youth in high income countries, accounting for 21% of total disease burden, and afflicting 1 in 10 youths in the US with severe impairment. Over 1,200 effective interventions, or evidence-based practices (EBPs), have been shown to improve the well-being of youth with psychiatric disorders. However, despite these advances, less than half of youths treated in community settings experience symptom improvement, a situation largely attributed to the low rates at which community providers adopt EBPs and, even when adopted, the low fidelity with which EBPs are implemented and sustained. Digital measurement-based care (MBC) systems, which collect treatment outcome data from patients and provide clinicians with real-time feedback and recommendations based on ?big data? actuarial algorithms, are a high-impact digital health technology EBP shown in 29 RCTs to generate improvements in clinical outcomes (i.e., d=.3-.5) across patient ages, diagnoses, and treatment modalities. Despite this, digital MBC systems are rarely used in community settings for youth, and when they are, fidelity and sustainment are often poor. Recent reviews indicate that many of these implementation and sustainment deficits can be traced to a lack of organization-level ?social infrastructure? or social contexts and leadership that do not support and motivate clinicians to adopt and use MBC systems; without this organizational social infrastructure, many implementation efforts fail. These observations are consistent with organizational climate theory and theories of behavior change which we have integrated to generate our primary hypothesis: achieving effective implementation and sustainment of MBC in community settings requires mechanisms of a strong organizational implementation climate and high clinician motivation generated through effective clinic leadership. With NIH support, we have pilot tested a highly transportable implementation strategy called Leadership and Organizational Change for Implementation (LOCI) that targets these mechanisms. Preliminary studies in mental health clinics show that LOCI is feasible, acceptable, and improves implementation leadership and climate. We propose a randomized controlled trial of LOCI in 20 children?s mental health clinics, incorporating 120 clinicians and a total of 720 youth outpatients, to test LOCI?s effects relative to implementation as usual (IAU) on clinician fidelity and youth clinical outcomes of a well-established digital MBC intervention during two phases of initial implementation and sustainment. This project brings together an early career/new investigator (Williams) collaborating with experienced, NIH funded implementation scientists (Aarons, Ehrhart) to advance programmatic research on the leadership, organizational, and clinician mechanisms that improve digital MBC implementation and sustainment. The study will (1) test LOCI?s effects on clinician fidelity to MBC and youth clinical outcomes during initial implementation, and (2) sustainment; and (3) test the multilevel mechanisms that link LOCI to MBC fidelity.